Reactivity local indexes

These generalized Fukui functions are local reactivity indexes, as they depend on the coordinates r where they are determined, in other words their values vary from one point to another within the molecule. It is clear that these quantities can be used to know how the charge or (and) spin densities respond when there are charge or (and) spin transfer to the reacting molecule. 

In this way, the SP-DFT using p,ps as variables set provides global and local reactivity indexes that give us the possibility to study processes that involve changes in the number of electrons, multiplicity (changes in the spin number), or both. Some examples are discussed in Section 10.4. 

Chatteijee, A. 2005. Application of localized reactivity index in combination with periodic DFT calculation to rationalize the swelling mechanism of clay type inorganic material. J. Chem. Sci. 117 533-539. 

The DA reactions between the electron-deficient diene 39 and the electron-rich ethylenes 33 and 40 and the electron-deficient ethylenes 11 and 15 have been reported by Spino et al. (see Scheme 2).37 The FMO theory was used to predict the reactivity of these reagents in DA reactions. These authors conclude that in the NED-DA reaction, the FMO theory could predict the relative reactivity, while in the case of the IED one, it could not.37 The high reactivity of the electron-deficient ethylene 11 with the electron-deficient diene 39 was studied using both the analysis of the potential energy surface for these cycloadditions and analysis of the global and local reactivity indexes.38 The analysis of... 

Santos, J.C., Chamorro, E., Contreras, R. and Fuentealba, P. (2004) Local reactivity index as descriptor ofbenzene adsorption in cluster models of exchanged zeolite-Y. Chem. Phys. Lett., 383, 612-616. 

In this sense, other authors propose a general hypothesis that any in vitro or in vivo biological activity can be explained only in terms of local reactivity indexes and tested for the inhibition cell growth by several 1-azabenzanthrone derivatives. In all of them, good structure -activity relationships have been obtained and some requirements for potent biological activity. This methodology to understand the whole process and, in the case of multi-step processes, is unable to relate the different reactivity indexes appearing in the SAR equations to any particular step [28]. 

Useful information about polarity of de DA processes may be obtained from the difference in the global electrophilicity power of the reactants. This difference has been proposed as a measure of the polar character of the reaction. On the other hand, local reactivity indexes are associated with site selectivity in a chemical reaction. These descriptors should reflect the sites in a molecule where the reactivity pattern stated by the global quantities should take place. For instance, an important local reactivity parameter was introduced by Parr et al., and it was defined as the Fukui fimction (Domingo, et al, 2002)... 

To describe the electrophilic character of a reactive site within a molecule, a local electrophilicity index [Pg.187]

One approach refers to local charge densities [188] the other one uses localization energies as a reactivity index [189]. In any event, the inductive effect of the methylene group, formed in the first protonation step, has to be taken into account if two sites provide comparable reactivity indices. 

Graphical Models are introduced and illustrated in Chapter 4. Among other quantities, these include models for presentation and interpretation of electron distributions and electrostatic potentials as well as for the molecular orbitals themselves. Property maps, which typically combine the electron density (representing overall molecular size and shape) with the electrostatic potential, the local ionization potential, the spin density, or with the value of a particular molecular orbital (representing a property or a reactivity index where it can be accessed) are introduced and illustrated. 

It can be noted that the local softness is obtained by multiplication of the Fukui function with the global softness the local softness can thus be considered as a weighted distribution of the global softness over the molecule. Due to this fact, the local softness should be used as a intermolecular reactivity index, whereas the Fukui function is an intramolecular reactivity index. The definition of local hardness is less trivial and remains a matter of current debate. 

Finally, just as we were able to define in Sect. 5 the nuclear softness, a local nuclear reactivity index in analogy with the electronic local softness, we can now introduce nonlocal nuclear reactivity indices in analogy to the electronic softness kernels [3], We define the nuclear softness kernels as follows... 

For benzo[. ]thiophene, there is a it-MO delocalization between the two aromatic rings. For benzo[r]thiophene, the orbitals of the five-membered rings are localized on the heteroatom, C-1 and C-3, and there is no it-MO delocalization on the heterocyclic five-membered rings. These results are in agreement with the theoretical aromaticity of these molecules as are theoretical results from the reactivity indexes. 

Orientation in electrophilic and nucleophilic reactions of aromatic compounds can be predicted with the aid of the reactivity index of MO theory. Electrophiles will attack positions of higher electron densities, larger superdelocalizability (electrophile), and the lower localization energy (electrophile). On the other hand, nucleophilic attack is preferred at positions of lower electron densities, larger superdelocalizability (nucleophile), and lower localization energy (nucleophile). Table XXIII shows reactivity indexes of some aromatic nitrogen cations. 

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